Cell diversity and organisation Flashcards
How do cells become specialised?
- some genes are expressed while others are silenced due to differentiation
- cells produce proteins that determine their structure and function
What is a transcription factor?
a protein controlling the transcription of genes so that only certain parts of the DNA are expressed in order to allow specialisation
How do transcription factors work?
1) move from the cytoplasm into the nucleus
2) bind to promoter region upstream of target gene
3) makes it easier or more difficult for RNA polymerase to bind to gene (increasing or decreasing transcription rate)
What is a stem cell?
undifferentiated cells that can divide indefinitely and turn into other specific cell types
Name and define the 4 types of stem cells?
Totipotent = can develop into any cell type (including placenta and embryo)
Pluripotent = can develop into any cell type (except placenta and embryo)
Multipotent = can develop into a few different types of cells
Unipotent = can only develop into one cell type
Suggest some uses of stem cells?
- repair damaged tissue
- drug testing on artificially grown tissues
- treating neurological diseases (e.g parkinson)
- researching developmental biology (e.g organ formation)
Describe 2 groups of specialised cells in blood?
Erythrocytes
- red blood cells
- biconcave no nucleus
- lot’s of haemoglobin to carry oxygen
Leucocytes
- white blood cells
- lymphocytes to engulf foreign materials
How do specialised cells in blood form?
multipotent stem cells in bone marrow
erythrocytes = with a short lifespan (unable to undergo mitosis as they have no nucleus)
lymphocytes = including neutrophil
State the relationship between a system and specialised cells?
specialised cells - tissues that perform specific function - organs made of several tissue types - organ system
Describe the structure of simple squamous epithelial cells?
- single smooth layer of squamous cells
- thin and flat with round nucleus
- fixed in place by basement membrane
Describe the structure of ciliated epithelial cells?
- column shaped with surface projections called cilia
- cilia move in a synchronised pattern
Describe the specialised structure of sperm?
- flagellum bound by plasma membrane propels cell
- spiral shaped mitochondria
- acrosome secretes enzyme to penetrate ovum coat
- haploid nucleus so fertilisation restores diploid chromosome number
Describe the structure and function of palisade cells?
- specialised to absorb light energy for photosynthesis
- contain many chloroplast
- pack closely together
Describe the structure and function of guard cells?
- form stomata
- when turgid stomata open, when flaccid stomata close
- walls are thickened by spirals of cellulose
Describe the structure and function of root hair cells?
Function:
- absorb water and low-concentrated mineral ions from the soil
Structure:
- hair like projections increase SA for osmosis
- many mitochondria producing ATP for active transport
What are meristems?
totipotent undifferentiated plant cells that can develop into various types of plant cells (including xylem and phloem)
Describe the structure of a vascular bundle?
strands of vascular tissue containing xylem and phloem vessels that distribute water and organic substances around the plant
Describe the structure of phloem of phloem tissue?
- sieve tube elements form a tube transporting sucrose in the dissolved form of sap
- companion cells involved in ATP production for active loading of sucrose into sieve tubes
- plasmodesmata are gaps between cell walls where the cytoplasm links allowing substances to flow
Describe the structure of vessel elements in xylem tissue?
lignified secondary walls for mechanical strength and waterproofing with perforated end walls for rapid water flow
Describe the structure of tracheids in xylem tissue?
tapered ends for close packing, pits for lateral water movement and contain no nucleus or cytoplasm
Describe the structure of cartilage?
- avascular smooth elastic tissue which produces extensive extracellular matrix (ECM)
- ECM mainly contains collagen and proteoglycan
Name 3 types of muscle in the body and where they are located?
cardiac = in the heart
smooth = walls of blood vessels and intestines
skeletal = attached to incompressible skeleton by tendons
Describe the structure of skeletal muscle?
- cells form bundles of parallel muscle fibres called myofibrils
- arrangement ensures no weakness points in the cell
- bundles surrounded by loose connective tissue with many capillaries
